What is under Hixson
In the early 1990s the U.S. Geological Survey studied the Cave Springs area for the local water utility. Its description of the ground is useful to anyone with a house on it. The rock is limestone and dolomite. Over the dolomite of the ridges lies a mantle of chert and clay which, in the wells the survey examined, was anywhere from 16 to 298 feet thick. Sinkholes and water-carved channels in the limestone were noted throughout the study area.
The area drains to North Chickamauga Creek and the Tennessee River, with Chickamauga Lake to the north and east and Walden Ridge rising on the west.
Ridge lot or low lot?
Which of the two you live on changes what an inspector expects to find.
On the ridge slopes
- Deep red clay with chert gravel, firm when dry
- Houses with a tall downhill wall, often on fill
- Pier depth hard to predict before installation
- Runoff from uphill is the usual source of trouble
On the low ground toward the creek
- Thinner clay over limestone, slower to drain
- More crawl spaces that take in water in wet spells
- Shallow piers settling into softened soil
- The setting where a depression in the yard deserves a second look
Why your neighbor's repair is no guide to yours
With the firm layer anywhere from a few yards to a few hundred feet down, two houses on the same street can need very different pier lengths. A sound proposal says what depth its price assumes and how extra depth is charged. If it does not, ask before signing.
Helical and push piers both report resistance as they go in, and the installer's log of those readings is the record that each pier reached something solid. Ask for a copy. The methods guide explains how the two kinds differ.
City or county? It decides the permit
Hixson is a community, not a city of its own. Much of it lies inside the Chattanooga city limits, where permits come from the Land Development Office. Addresses beyond the limits are handled by Hamilton County Building Inspection. If you pay Chattanooga city property tax you are inside. If you are unsure, either office can tell you from the address.